Lipids

• Lipid are organic compounds that contain carbon, Hydrogen & oxygen atoms which form the framework for the structure & functional of living cells.

OR

• Any of the large group of natural substances that do not dissolved in water such as natural oils & waxes.

  OR

• Lipids may be regarded as organic substance relatively insoluble in water soluble in organic solvent.

STRUCTURE OF LIPIDS

• Lipids are made up of two molecules Glycerol & fatty acids.

• Glycerol molecules consist of three carbon atoms with a hydroxyl group attached to it & fatty acid are the long chain of hydrocarbons with a carboxylic acid group at the end.

• Lipids are the polymerase of fatty acids that contain a long, no-polar hydrocarbon chain with small polar region containing oxygen.

CLASSIFICATION OF LIPID

• Flow chart on lipid:

  https://assets.zyrosite.com/AzG8ZkQ8NDU2ebR1/flow-chart-on-lipid-m2Wr4l4L7XC2RjMl.pdf

• Lipids are mainly classified into three types –

- Simple lipids

- Complex lipids

- Derived lipids

1. Simple lipids

• Simple lipids are triglycerides, ester of fatty acids & wax esters. The hydrolysis of these lipids gives glycerol & fatty acid.

• Simple lipids are divide as –

  - Triglyceride

  - Waxes

  A. Triglyceride:

  • It is a lipid molecule that formed one glycerol molecules associated with three fatty acids molecules.

  • They are constituents of fats & oils.

  • Lipid that is solid at room temperature are fats & lipid that are liquid at room temperature are oil.

a. Glycerol –

o It is colourless, viscous lipid that is sweet tasting & non- toxic.

o It is simple polyol compound.

b. Fatty acids

o Fatty acids are carboxylic acid with hydrocarbon side chain

o They are simplest form of fatty acids

o Long chain of hydrocarbon with a carboxylic group at the end

o Fatty acid are an important component of lipid they are building block of fat in the body

o They are of two types –

(I) Saturated fatty acids:

o It consist of single c-c bonds.

o These molecules fit closely together in a regular pattern & strong attraction between fatty acids chain.

o These fatty acids have high melting points, which make them solid at room temperature.

o Example – palmitic acid, steoric acid

(II) Unsaturated fatty acids:

o Unsaturated fatty acid are the fatty acid that consist one or more C = C double bond.

o It divide into two classes

§ Mono polyunsaturated fatty acids

Example – oleic acid

§ Poly unsaturated fatty acids

Example – linoleic acid

# Role of Fats

• Fat play essential role in body.

• Absorptions & transportation

• Produce energy in the form of hydrogen

• Structural component of cells

• Produce & regulate hormone

• Maintain blood pressure

• Control cholesterol

B. Waxes:

o Waxes are usually saturated with long chain monohydric alcohols.

o They are simple ester of fatty acids

o Examples –

- Beeswax

- Spermaceti

2. Complex lipids:

• Complex or compound lipids are the ester of fatty acids with group along with alcohol & fatty acids.

• Examples –

- Phospholipids

- Glycolipids

A. Phospholipids:

o They contain phosphoric acid & frequently a nitrogenous base.

o This is in addition to alcohol & fatty acids.

B. Glycolipid:

o These lipid contain a fatty acids carbohydrate & nitrogenous base.

3. Derived lipid

• Derived lipids are the hydrolyzed component of simple & complex lipids

A. Steroids:

o Steroids are found in the cell membrane & have fused ring structure, many steroids have –OH functional groups.

o They are also hydrophobic & insoluble in water

o Steroids also act as hormones in the body.

B. Sterols:

o They are widely present in plants & animals such as cholesterol

o They are subgroup of steroids

o Found in animals

o Used to make bile for digestion in the body

C. Carotenoids:

o They are lipid solube component

o They are pigment that are mainly responsible for many of the yellow & red colur of plant & animals products.

o It consist carotenes & xanthophylls

o It is important in the health of human eye.

PROPERTIES OF LIPIDS

PHYSICAL PROPERTIES

• Lipids are oily or greasy non-polar molecule

• Lipids stored in the Adipose tissue in the body

• Lipid are heterogenous group of compound mainly composed of hydrocarbon chains

• Soluble in non-polar solvent & insoluble in water

• Poor conductor or heat & electricity

• Colorless, tasteless & odorless in their pure state

CHEMICAL PROPERTIES

• Hydrolysis of fats & oils

• Reserve of esterification

• Oils are liquid at room temperature

• Fats are semisolids